Coal processing

ABSTRACT

A METHOD FOR FORMING A LOW SULFUR RESIDUAL FUEL OIL FROM A HIGH SULFUR COAL COMPRISING HYDROGENATING THE COAL IN THE ABSENCE OF EXTERNALLY SUPPLIED CONTACT PARTICLES AND AT AN ELEVATED TEMPERATURE, FOLLOWED BY SEPARATING SOLID PARTICLES FROM THE LIQUEFIED COAL AT AN ELEVATED TEMPERATURE.

y 1972 H. E. JACOBS ET 3,663,420

COAL PROCESSING Filed Oct. L4, 1970 SOLVENT GAS GAS s IO 16 3 l 8 |2 I4 '5 1 COAL z L4 I F5 7 9 H I H2 souos RESID FUEL 2o +RL M.M

INVENTOR HARRY 5. JACOBS GEORGE R. WON/FELL ATTORNEY 3,663,420 COAL PROCESSING Harry E. Jacobs, Glenwood, Ill., and George R. Worrell,

Media, Pa., assignors to Atlantic Richfield Company,

New York, N.Y.

Filed Oct. 14, 1970, Ser. No. 80,673 Int. Cl. Cg N04 US. Cl. 208-8 6 Claims ABSTRACT OF THE DISCLOSURE A method for forming a low sulfur residual fuel oil from a high sulfur coal comprising hydrogenating the coal in the absence of externally supplied contact particles and at an elevated temperature, followed by separating solid particles from the liquefied coal at an elevated temperature.

BACKGROUND OF THE INVENTION Heretofore solid coal has been liquefied by hydrogenating same in the presence of a solid particulate hydrogenation catalyst which is sometimes described as catalytic contact particles.

A particularly useful process is that wherein the externally supplied contact particles are set up in an ebullated bed as fully and completely disclosed in US. Patent Re. 25,770, the disclosure of which is incorporated herein by reference.

These processes are designed to maximize the production of naphthas, gasolines, and the like. Accordingly, the amount of residual materials produced are mininized.

As a consequence of increased emphasis upon pollution free fuels, particularly low sulfur fuels, the heretofore generally undesirable residual fuel oil, i.e., a complex hydrocarbonaceous oil having a boiling range which starts at about 600 F., has increased substantially in demand. This is especially so if the fuel oil also has a low sulfur content. Thus, low sulfur residual fuel oils have been replacing higher sulfur coal as an energy source, i.e., in the generation of electricity, and therefore now enjoys a status of much greater demand than heretofore, particularly in their relation to naphthas, gasolines, and the like.

SUMMARY OF THE INVENTION According to this invention there is provided a method for maximizing the formation of low sulfur (no greaterthan 1 weight percent sulfur) residual fuel oil from a high sulfur (greater than 1 weight percent sulfur) solid coal so that the raw coal is still the energy source but in the transformed and more acceptable status of a low sulfur hydrocarbonaceous liquid fuel.

According to this invention the coal is hydrogenated in the absence of externally supplied contact particles and at a temperature of at least about 500 F. thereby at least partially gasifying and liquefying the coal.

The liquid product from the coal contains solid particles such as unconverted coal particles, ash, char, coke, and the like. The solid particles are separated from the liquid product while the liquid product is at an elevated temperature not less than 200 F. below the temperature at which the coal was hydrogenated. The solids free liquid product is useful as a low sulfur residual fuel oil.

Advantageously, in the particular process of this invention desulfun'zation is also achieved so that there is a two-fold improvement obtained at the same time, i.e., desulfurization and the production of the desired residual fuel oil.

By the combination of a hydrogenation reaction in United States Patent 0 3,663,420 Patented May 16, 1972 the absence of hydrogenation catalyst or other particulate contact particles with the particular hot solids separation step of this invention, not only is the residual fuel oil product maximized in amount and desulfurized, but, in addition, the residual fuel oil is made amenable to conventional distillation and/or hydrocracking processes to produce gasoline, naphtha, and the like should this be economically desirable.

In addition, by employing an empty hydrogenation reactor as regards particulate contact material, longer residence times for the coal, hydrogen, etc. are obtainable because there is a greater volume available in the same size reactor when the contact particles are absent. Therefore, for the same residence time a much smaller reactor can be employed in this invention. The smaller volume requirement for the reactor coupled with the flexibility and configuration for the reactor (being capable of being disposed horizontally as a tube type reactor) allows for a much greater variety of apparatus in carrying out the method of this invention.

Further, there is the additional advantage that by following the method of this invention the desired low sulfur residual fuel oil product is obtained with less hydrogen consumption as compared to catalytic hydrogenation processes and the like.

Accordingly, it is an object of this invention to provide a new and improved method for maintaining high sulfur coal as an energy source. It is another object to provide a new and improved method for obtaining maximum amounts of low sulfur residual fuel oil from a high sulfur solid coal. It is another object to provide a new and improved process for producing residual fuel oil containing no more than 1 weight percent sulfur based on the total weight of the residual fuel oil. It is another object to provide a new and improved method for gasifying and/or liquefying normally solid coal in the absence of externally supplied contact particles be they catalytic or inert.

Other aspects, objects, and advantages of this invention will be apparent to those skilled in the art from this disclosure and the appended claims.

DETAILED DESCRIPTION OF THE INVENTION The drawing shows a diagrammatic representation of apparatus useful in practicing this invention.

More specifically, the drawing shows a hydrogenation reactor 1 which is initially completely empty and therefore can be an elongated furnace tube disposed horizontally or vertically or at any angle in between and can be the reactant heater as well as the reactor.

Thus, the reactor in this invention is much more flexible in configuration and design than, for example, an ebullated bed reactor.

Raw subdivided coal is supplied by pipe 2 and a slurrying medium (solvent) is supplied by pipe 3, the coal and solvent being mixed to form a conventional coal-slurry which passes by way of pipe 4 into reactor 1.

Molecular hydrogen and/or a hydrogen donating gas and/or liquid is supplied to reactor 1 by way of pipe 5. As an example, heating medium can be supplied by way of pipe 6 to an outer jacket around reactor 1 to provide the heat for reactor 1, the cooled heating medium being removed from the jacket by pipe 7. Any suitable means for supplying heat to reactor 1 can be employed.

The reaction products, both gaseous and liquid, are removed from reactor 1 by pipe 8 and passed to a hot separation unit 9 wherein the liquid is held for a sufiicient time to allow the gas to separate therefrom and be removed by way of pipe 10.

The degasified liquid hydrocarbonaceous product of the hydrogenation reaction contains solid particles such as unconverted coal and the like. This liquid is passed by way of pipe 11 to a separation zone 12' which is operated under certain elevated temperature requirements hereinafter described and which separates the solid particles from the liquid, the solid particles being removed by way of pipe 13 and the substantially solids free liquid product passing by way of pipe 14 to gas-liquid separator 15 wherein additional gas is removed by way of pipe 16. The gases from pipes and 16 can be combined if desired for further processing.

The solids free liquid removed from separator by way of pipe 17 can be employed as a residual fuel oil.

Separator 15 can be employed as an atmospheric or vacuum distillation operation wherein materials boiling below 600 F. are removed so that the residual fuel oil in pipe 17 is composed essentially of materials which have a boiling point starting at 600 F. and preferably has a boiling range of from about 600 to about 1000 F.

Depending upon the particular raw coal feed, the particular hydrogenation conditions, and the solids separation step, fractionation step 15 may or may not be employed and the desired low sulfur residual fuel oil product still obtained. In other words, in various situations the liquid product in pipe 14 can be employed as the residual fuel oil product. Similarly, as desired, the liquid hydrocarbonaceous product in pipe 14 can be passed in part by way of pipe 20 to pipe 4 for re-introduction to reactor 1 to help control the solids content in reactor 1.

The gases from pipes 10 and 16, either separately or combined, can be further processed to recover gasoline, naphtha, light distillate fuel, and the like, but the majority of the product from this process will be heavier materials-primarily residual fuel oil.

Water in the form of cooled, ambient, or heated liquid and/or steam can be added to one or more of reactor 1 and pipes 2 through 5 and 20 as an aid in the hydrogenation process. Additionally or alternatively, the raw coal feed in pipe 2 can be deliberately wet with Water or can be wet as received from its transportation means to pipe 2. Along this line, the coal can be put into pipe 2 wet with water as mined or as upgraded or comminuted at the mine or other processing plant prior to transportation to pipe 2. Generally, the amount of Water added will constitute from about 0.1 to about 50 weight percent water based on the total weight of the coal being added to reactor 1.

Substantially any coal can be employed, for example, semi-anthracite, bituminous, semi-bituminous sub-bituminous, lignite, peat, mixtures thereof, and the like. The coal should be comminuted so that at least about 90 weight percent passes an 8 mesh (Tyler) sieve.

The slurrying medium can be a liquid hydrocarbonaceous material produced by reactor 1, e.g., the liquid product in pipe 14, and/or hydrogen-donor liquid such as Tetralin, or partially hydrogenated 3 or 4 ring aromatics such as naphthalene, anthracene, phenanthrene, and the like. Other hydrogen-donor mediums may be attained by hydrogenation of the hydrocarbonaceous liquid P oducts of reactor 1. Such a medium would boil within the range of from about 400 to about 950 F. The hydrogen-donor liquids are optional fiom a hydrogenation standpoint because adequate hydrogenation can be obtained from molecular hydrogenation alone or whatever other type of hydrogen donating material is supplied by way of pipe 5.

The comminuted coal is mixed with the slurrying medium preferably in solvent/coal weight ratio as added to reactor 1 of from about 0.1/1 to about 4/1. The solvent part of the coal slurry can be formed completely or partially from externally added solvent from pipe 3 or hydrocarbonaceous liquid product from pipe 14, or hydrocarbonaceous liquid product from other processes such as the hydrogenation of oil, tar, and the like, or combinations of two or more thereof as desired. The hydrogenating material added by way of pipe 5 is charged in amounts such that the hydrogen partial pressure in reactor 1 is maintained at from about 400 to about 3000 p.s.i.a., preferably from about 500 to about 2250 p.s.i.a.

Reactor 1 is operated at a temperature of at least about 500 F., preferably at a temperature of from about 500 to about 1000 F., with a total pressure in the reactor of from about 400 to about 5000, preferably from about 500 to about 3000, p.s.i.g.

The combined gaseous and liquid products from reactor 1 are subjected to a conventional gas-liquid separation step for the removal of substantially all of the gaseous product. The gas separation step can be carried out at ambient or subambient pressures as desired. It is also carried out on the heated products as they issue from reactor 1.

The substantially degasified liquid product is then subjected to a hot solids separation step for removal of solid particles therefrom. It is important to the results of this invention that the hot separation step be carried out at an elevated temperature not less than 200 F. below the hydrogenation temperature of reactor 1, preferably not less than 200 F. below the hydrogenation temperature and not substantially above that hydrogenation temperature. For example, separation can be carried out at from about 300 to about 1000 F. when the reaction temperature range is from about 500 to about 1000 F. It is also preferred that the hot separation step be carried out at a pressure of from about 400 to about 5000 p.s.i.g., preferably in the range of from about 500 to about 3000 p.s.i.g. when this is the pressure range for the hydrogenation reactor 1. It is still more preferred that the solids separation step be carried out at substantially the same pressure as the hydrogenation step of reactor 1.

The solid separation step can employ any process and apparatus which will substantially remove the solid particles from the liquid product and preferably employs gravity separation, filtering, centrifugation, or combinations thereof. For example, a conventional liquid cyclone (hydroclone) or a pressure rotary filter or pressure batch filter or combinations thereof can be employed so long as substantially all the solid particles present in the liquid product are removed therefrom.

The product in pipe 14 can then be subjected to fractionation for the further removal of materials boiling below 600 F., the fractionation employing any desired process including liquid-liquid or gas-liquid extraction, fractional distillation either atmospheric or vacuum, and the like.

Example I Illinois No. 6 coal was processed to form residual fuel oil using substantially the apparatus and the flow scheme as shown in the drawing.

The coal was comminuted to a minus and plus 325 mesh (Tyler) particle size range, and mixed with a solvent composed of hydrocarbonaceous oil boiling above 400 F. taken from pipe 14 in a solvent/coal addition weight ratio of 1/1.

The coal slurry was charged to an empty tube type reactor at a space velocity of 18.7 pounds of coal per hour per cubic foot of reactor and subjected to hydrogenation with molecular hydrogen at a temperature of 850 F. and a total pressure of 2250 p.s.i.g. The reaction time was 1.7 hours.

The liquid product, heated as received from the hydrogenation reactor, was passed to an atmospheric gas-liquid separator wherein the gas was allowed to separate therefrom and be removed overhead.

The degasified liquid product was then passed to a batch pressure filter which removed all particles down to 1 micron size.

The portion of the solids free liquid that was not returned to form coal slurry was passed to an atmospheric distillation unit wherein materials boiling at 650 F. and below were removed in the gaseous state and the liquid remaining, i.e., all materials boiling at 650 F. and higher were removed as the low sulfur residual fuel oil. This residual fuel oil product contains about 0.4 weight percent sulfur based on the total weight of the fuel oil whereas the raw coal used in preparing the coal slurry originally contained about 3.5 weight percent sulfur based on the total weight of the dry coal.

The amount of fuel oil produced having a boiling range that starts at about 650 F. was 34.1 weight percent (based on the total weight MAP) of the coal charged and the hydrogen consumption was 3.3 percent. These results are compared to a run carried out under the same conditions as set forth above except that the reactor contained cobalt molybdate hydrogenation catalyst subdivided to be in the particle size range of minus 100 to plus 200 mesh (Tyler), the catalyst forming an ebullated bed in the hydrogenation reactor. The ebullated bed contains about 50 weight percent catalyst solids. In such a catalytic run the amount of liquid hydrocarbonaceous product having a boiling range that starts at about 650 F. was 31.2 weight percent based upon the weight of the coal charged MAE (moisture and ash free coal) and the hydrogen consumption was 4.4 weight percent based on MAP coal.

Example II The catalyst empty reactor process of Example I was substantially repeated using instead Pittsburgh A seam coal containing 4.4 weight percent MAF sulfur under the following conditions:

TABLE 1 Coal feed, pounds of coal/hour/cubic foot of reactor 31.2 Coal oil slurry medium, pounds/pound of coal 4.2/1 Temperature, F. 850 Pressure, p.s.i.g 2250 H rate, thousands of standard cubic feet/ton of coal 54 The results of this run were:

TABLE 2 Liquid residuum boiling at 975 F. and higher 1 60.8 H consumption 1 2.3 Sulfur content 1 1 1 Weight percent MAE coal.

A catalytic run was made using the catalyst of Example I and the conditons of this example except that the coal oil ratio was 4.4/1 pounds per pound of coal and the H rate was 61.

The results were:

TABLE 3 Liquid residuum boiling at 975 F. and higher 1 38.1 H consumption 1 6.7 Sulfur content 1 0.7

1 Weight percent MAF coal.

Example III The noncatalyst process of Example II was substantially repeated except that the coal oil ratio was 1/ 1 pounds per pound of coal, the temperature was 851 F., and the H rate was 31,000 standard cubic feet per tone of coal.

The results were:

TABLE 4 Liquid residuum boiling at 975 F. and higher 1 28.5 H consumption 1 3.8 Sulfur content 1 0.5

1 Weight percent MAE coal.

Thus, it can be seen that according to this invention the amount of low sulfur residual fuel oil obtained is maxirnized with reduced hydrogen consumption and eliminated catalyst cost.

Reasonable variations and modifications are possible within the scope of this disclosure without departing from the spirit and scope of this invention.

We claim:

1. A method for forming a low sulfur residual fuel oil from a high sulfur coal which contains greater than 1 weight percent sulfur based on the total weight of the coal comprising forming a subdivided coal-solvent slurry wherein said coal is subdivided so that at least about weight percent thereof passes an 8 mesh sieve and is retained on a 325 mesh sieve, said subdivided coal and solvent are mixed in a solvent/coal weight ratio of from about 0.1/1 to about 4/ 1, and said solvent is at least one of a hydrogen donor hydrocarbonaceous liquid and a hydrocarbonaceous oil derived from a coal and/or oil hydrogenation process, hydrogenating said coal in said slurry in the absence of externally supplied hydrogenation catalyst and other externally supplied contact particles and at a temperature of from about 500 to about 1000 F. a pressure of from about 400 to about 3000 p.s.i.a. to at least partially gasify and liquefy said coal, separating the gas product from the liquid product, the liquid product containing solid particles, separating said solid particles from said liquid product using gravity separation, filtering, centrifugation, or a combination thereof and while said liquid product is at an elevated temperature not less than 200 F. below the hydrogenation temperature, and fractionating said solids free liquid product to remove therefrom substantially all the remaining materials which boil at less than 600 F., whereby the final solids free liquid product is a low sulfur residual fuel oil which contains no more than 1 weight percent sulfur based on the total weight of the residual fuel oil and has a boiling range that starts at about 600 F.

2. A method according to claim 1 wherein said particle separation is carried out while said liquid product is at a temperature of from about 300 to about 1000 F. using gravity separation, filtering, centrifugation, or a combination thereof.

3. A method according to claim 1 wherein said particle separation is carried out while said liquid product is at a temperature no lower than 200 F. below the hydrogenation temperature and not substantially above said hydrogenation temperature, and at a pressure of from about 400 to about 5000 p.s.i.g.

4. A method according to claim 3 wherein said pressure is substantially the same as the hydrogenation pressure.

5. A method according to claim 1 wherein said fractionation comprises at least one distillation operation to remove the materials boiling at less than 600 F. substantially in the gaseous state.

6. A method according to claim 5 wherein said at least one distillation operation is an atmospheric distillation.

References Cited UNITED STATES PATENTS 3,518,182 6/1970 Paterson 2088 2,308,247 1/1943 Pott et a1 208--8 3,109,803 11/1963 Bloomer et a1 2088 3,375,188 3/1968 Bloomer et a1 2088 DELBERT E. GANTZ, Primary Examiner V. OKEEFE, Assistant Examiner 

